The three at the top of the list, the STK681-300, 310 and 320, have current sensing resistors built-in. The bottom two, the STK681-332 and 352 include protection against short to ground and short to supply built-in. This is difficult to implement with discrete devices, as there must be detection circuitry and logic, and its operation must be carefully verified. Therefore, designing the discrete solution is costly and time-consuming.